1. Field of the Invention
The present invention pertains to the field of refrigeration apparatus and is more particularly directed to a high efficiency ice making machine having an improved ice harvesting mechanism including a fail safe mechanism to prevent minimize inconvenience and down time due to blockage of the ice delivery opening and consequent accumulation of ice within the harvesting mechanism.
2. State of the Prior Art
Various designs for ice making machines are known as exemplified by the following patents:
______________________________________ U.S. Pat. No. Patentee Issue date ______________________________________ 3,921,415 Kattis November 25, 1975 3,159,010 Kattis December 1, 1964 3,320,769 Ross May 23, 1967 2,575,374 Walsh November 20, 1951 3,620,040 Clearman et al November 16, 1971 3,797,271 Wanson March 19, 1974 ______________________________________
Also known to the applicant and relevant to the drive mechanism of the present invention are:
______________________________________ 2,199,038 Brix-Hansen April 30, 1940 1,954,518 Downer April 10, 1934 ______________________________________
In general, the Kattis and Ross ice making machines disclosed by the above referenced patents include an evaporator assembly surrounded by a tank connected to a water supply conduit. A liquified refrigerant gas is supplied to the interior of the evaporator where it is allowed to evaporate and absorb heat from the water surrounding the evaporator. A layer of ice thus forms on the outer surface of the evaporator. An auger or mechanical scraper is mounted for rotation about the evaporator and spaced from its outer surface such that when the layer of ice attains a given thickness the auger breaks off the ice in the form of cracked or flake ice which tends to float within the water tank. Various mechanisms are provided for harvesting the ice, that is, collecting the ice broken away from the evaporator surface and delivering it to the exterior of the ice making machine. The harvesting mechanisms in the ice making machines of the prior art suffer from a common shortcoming in that the ice is pushed against gravity along an upwardly sloping ramp, rising from the water tank and terminating in a chute through which the ice is delivered into a hopper or suitable container. The machines of the prior art thus rely on the pressure exerted by accumulation of freshly made ice to push previously formed ice up the ramp chute and out of the machine.
It is well known that fragments of ice are readily cemented together into a hard solid mass when the fragments are pressed together. Thus it is critical in an effective ice making machine to minimize the handling of large quantities of ice which through its own weight will have a tendency to stick together in a cohesive mass, or to push or otherwise exert pressure on any substantial quantity of ice. This has a tendency of compacting the ice and if the delivery chute becomes blocked for any reason, the harvesting mechanism continues to operate, compacting the ice at ever increasing pressures until the system jams completely and ceases to operate. The pressures exerted by the ice can be such as to snap off the drive shaft which rotates the auger or to break some other portion of the mechanism, requiring extensive and costly repairs. Even if no mechanical damage is sustained by the device, the accumulation of compacted ice requires that the ice making machine be defrosted and the accumulated ice melted before operation can resume. This deicing may require several hours of idle machine time.